Injectable collagen, patented by the Collagen Corporation under the trade names Zyderm and Zyplast, is derived from purified bovine collagen. The purification process creates a product similar to human collagen. Injectable collagen received approval from the Food and Drug Administration in 1981. It is produced in various thicknesses to meet individual patient needs.

Collagen is used primarily to fill wrinkles, lines and scars on the face and sometimes the neck, back and chest.

Because the anesthetic agent lidocaine is mixed in with collagen, additional anesthetic is usually not used. However, if you are especially sensitive to pain, your doctor may use a topical cream anesthetic or a freon spray to numb the injected area. Or, you may elect to have an injected local anesthetic or sedative drugs.

Treatment with collagen can begin after a skin test determines that you're not allergic to the substance. The collagen is injected using a fine needle inserted at several points along the edge of the treatment site. If a local anesthesia has not been used, you may feel some minor stinging or burning as the injections are administered.

Since part of the substance is salt water that will be absorbed by the body within a few days, your doctor will slightly overfill the area. You may be asked to hold a hand mirror during the procedure to help your doctor decide when you've had enough.

Immediately following treatment, you may notice some minor discomfort, stinging or throbbing in the injected area. Occasionally some bruising or swelling will occur, but it is usually minor. Any redness that appears in the injected site usually disappears within 24 hours. However, in some individuals, particularly fair-skinned patients, this redness may persist for a week or more. Tiny scabs may also form over the needle-stick areas; these generally heal quickly.

No bandaging is needed and you are free to eat, drink and wear makeup with sunblock protection shortly thereafter. There may be some temporary swelling and redness in the treated area, which should dissipate within a few days. If these symptoms persist, contact your surgeon.

The duration of results from collagen injections is variable. Collagen's longevity depends on the patient's lifestyle and physical characteristics as well as the part of the body treated. In general, the injected material is likely to disappear faster in areas that are more affected by muscle movement.